Hydrogenated polymers with a radial structure having a core based on calixarenes and use thereof in lubricant compositions

ABSTRACT

Hydrogenated polymers with a radial structure having a core made up of calixarenes of the general formula (I), to the core of which is linked a number P of hydrogenated linear polymer segments selected from: —hydrogenated homopolymers or copolymers of conjugated dienes; or —hydrogenated copolymers of said conjugated dienes and monoalkenyl arenes, and —mixtures thereof said formula (I) in which: —R 1 , R 2 , R 3  and R 4  are independently selected from hydrogen; a group containing carbon and hydrogen; a group also containing heteroatoms in addition to carbon and hydrogen; a group also containing silicon in addition to carbon, hydrogen and heteroatoms; —one of the two substituents R 5  and R 6  is hydrogen, while the other may be hydrogen or alkyl, with a number of carbon atoms between 1 and 6, preferably methyl and ethyl; —n is an integer in the range between 4 and 16.

This application is a 371 of PCT/IB2015/052776, filed Apr. 16, 2015.

The present invention relates to hydrogenated polymers with a radialstructure having a core based on calixarenes and to the method for thepreparation thereof.

The polymers provided by the present invention may be used as viscosityindex-improver additives in lubricant compositions.

In the present patent application, all the operating conditionsmentioned in the text should be taken to be preferred conditions even ifthis is not explicitly stated.

For the purposes of the present explanations, the term “comprise” or“include” also encompasses the term “consist in” or “essentially consistof”.

For the purposes of the present explanations, unless stated otherwise,range definitions always include the extremes.

In the present patent application, radial polymers are also known anddenoted as star polymers.

It is known that the viscosity of lubricating oils varies withtemperature. Many lubricating oils have to be used over a widetemperature range and it is thus important for the oil not to be tooviscous at low temperature and not to be too fluid at elevatedtemperature. An oil's variation in viscosity with temperature isexpressed by the value of the viscosity index. The higher is theviscosity index, the lower is the oil's variation in viscosity withtemperature.

It is known to use polymer-based additives for the purpose of increasingthe viscosity index of lubricating oils, so increasing the viscositythereof at elevated temperature and as far as possible limiting anyincrease in low-temperature viscosity. Polymers which are usually usedfor improving the viscosity index are: ethylene-propylene copolymers,hydrogenated conjugated polydienes (e.g. hydrogenated polyisoprene),hydrogenated styrene-butadiene copolymers, hydrogenated styrene-isoprenecopolymers and poly(alkyl methacrylates). The synthesis of linearhydrogenated polymers of conjugated dienes and of linearstyrene-conjugated diene copolymers and the use thereof in lubricantsare described, for example, in U.S. Pat. Nos. 3,554,911; 3,668,125;3,772,196; 3,775,329; 3,835,053; EP 585269 and EP 578725. For each ofthe above-stated classes of polymers, as molecular weight rises, so toodoes the thickening power and thus the quantity of polymer required toachieve a specific increase in viscosity of the oil at elevatedtemperature (thickening) falls. If a polymer is to be a good additivewhich improves the viscosity index, it must not only have a beneficialinfluence on the viscosity index of the fresh oil, but must also bestable and retain its function when the oil is in use in an engine. Forthis reason, a good additive must also have mechanical shear stability.It is known that the mechanical shear stability of a polymer falls withincreasing molecular weight and thus selecting an additive whichimproves the viscosity index is usually a compromise between using largequantities of low molecular weight polymers which are resistant tomechanical shear and using small quantities of high molecular weightpolymers which have poor resistance to mechanical shear.

It is furthermore known that the viscosity index-improver additives usedin lubricating oils may contribute to varnish and carbon depositformation in those parts of the engine which are exposed to elevatedtemperatures. The additives to be preferred will therefore be thosewhich ensure a good thickening power and good shear stability with theminimum quantity of polymer.

U.S. Pat. No. 4,116,917 discloses a class of hydrogenated radial (star)polymers made up of a core of polydivinylbenzene (PDVB) to which areradially linked at least 4, preferably from 7 to 15, linear segments ofhydrogenated conjugated polydienes or of hydrogenated styrene-conjugateddiene copolymers.

Said radial polymers make it possible to increase thickening power whenhot, to reduce the effect on lubricant viscosity when cold and toincrease the mechanical shear stability of said additives. The methodused for synthesising such star polymers is known as “arm first, corelast” and provides: (a) anionic polymerisation of a conjugated diene orcopolymerisation of a conjugated diene and styrene to form a livinganionic polymer; (b) adding divinylbenzene to the living anionicpolymer, initially forming a PDVB core, the vinyl groups of which arecapable of reacting with the living anion so forming the star polymer;(c) hydrogenating the star polymer. Using such star polymers makes itpossible to reduce, relative to known prior art polymers, the quantityrequired to achieve a specific thickening and a specific mechanicalshear stability of the lubricating oils. The viscosity index-improveradditives containing the star polymers disclosed in U.S. Pat. No.4,116,917 are marketed by Infineum International Ltd.

Said class of radial polymers does, however, have a number of negativecharacteristics primarily associated with the PDVB core which:

-   -   has a crosslinked gel structure which is not well defined;    -   complicates control of the number of linear polymer segments        linked to the core, so bringing about a certain degree of        variability in the structure and characteristics of the radial        polymer, such as for example mechanical shear stability and        thickening.

Furthermore, making industrial use of divinylbenzene is problematic dueto its elevated reactivity and tendency to give rise to unwantedpolymerisation reactions.

It is thus desirable to obtain polymers made up of a core with awell-defined structure in such a manner as to have a well-defined numberof polymer segments linked to said core.

Two different methods are known for obtaining star polymers having acore with a well-defined structure:

-   (1) using multifunctional initiators, a method known as “core first,    arm last”,-   (2) using multifunctional reagent molecules capable of linking to    the functional groups of previously formed polymers, a method known    as “arm and core first”.

Using multifunctional initiators to synthesise star polymers by anionicand cationic polymerisation is a method which is well-known, but notvery widely used, due to problems with the solubility of themultifunctional initiator, especially in anionic polymerisationreactions.

In contrast, there are various prior art examples of usingmultifunctional reagents to synthesise star polymers by the “arm andcore first” method. Examples of types of such multifunctional reagentswhich have been used as the core for obtaining star polymers aresiloxanes, to which cationically-obtained polyisobutylene segments arelinked by hydrosilylation reactions, and alkoxysilanes and halosilanes,to which living anionic polymer chains are linked by anionicpolymerisation. Siloxanes, however, have the disadvantage of having lowthermal and oxidation stability, while alkoxysilanes and halosilaneshave the primary disadvantage of giving rise to the formation of starpolymers made up of at most four polymer segments linked to the siliconcore.

A further type of multifunctional reagents, which are generallycharacterised by a larger number of reactive functional groups and byexcellent thermal and oxidative stability, are the calixarenes which arecyclic products derived from the condensation of p-substituted phenolsand formaldehyde. Various calixarene compounds and the associatedprocesses for the preparation thereof were developed by Gutsche and arementioned for example in Houben-Weyl 6, 1036 and in the book “Monographsin Supramolecular Chemistry”, Series Editor J. Fraser Stoddart,published by the Royal Society of Chemistry in 1989 and 1998.

U.S. Pat. No. 5,840,814 describes radial polymers having numerouswell-defined arms linked to a well-defined core and the synthesisthereof (in the prior art, radial polymers are also known as starpolymers).

The core is made up of a calix[n]arene, in which n ranges from 4 to 16,and the derivatives thereof, to which are connected at least threepolymer arms.

Said polymer arms are preferably selected from polyisobutylene,polysiloxanes, in particular polydimethylsiloxane, or both.

U.S. Pat. No. 5,840,814 furthermore describes the synthesis methods forsuch radial polymers.

A first method provides that the polyisobutylene arms with terminalhydroxyl groups (—OH) are linked to the calixarene core which is made upof from 4 to 16 units and which includes at least one ester functionalgroup for each unit, to which the polyisobutylene is linked bytransesterification in the presence of a catalyst.

A second method provides that the polysiloxane arms, preferablypolydimethylsiloxanes, with terminal Si—H groups are linked to thecalixarene core which is made up of from 4 to 16 units and whichincludes at least one allyl functional group for each unit, to which thepolysiloxane is linked by hydrosilylation in the presence of a catalyst.

A third method provides that the polyisobutylene arms with terminalhydroxyl groups (—OH) and the polysiloxane arms with terminal Si—Hgroups are linked to the calixarene core which is made up of from 4 to16 units and which includes at least one ester functional group for eachunit to which the polyisobutylene is linked by transesterification inthe presence of a first catalyst, and an allyl functional group for eachunit to which the polysiloxane is linked by hydrosilylation in thepresence of a second catalyst.

U.S. Pat. No. 5,840,814 does not show examples of using the above-statedpolymers in engine oils, and furthermore such products have thedisadvantage of not being particularly suitable for use as additives forimproving the viscosity index of lubricating oils. This is because it isknown that polysiloxane-based polymers are not used for such anapplication and that polyisobutylene (PIB)-based products are notparticularly effective in improving the viscosity index of oils, in thatthey have a good thickening power when hot, bringing about an increasein the viscosity at elevated temperature of the lubricating oil to whichthey are added, but they do not exhibit good behaviour when cold in thatthey also bring about an increase in the low-temperature viscosity ofthe oil. This behaviour complicates the use of such polymers forformulating lubricating oils of SAE 0W, 5W and 10W viscosity grades forwhich stringent limits are set for low-temperature viscosity values (CCS(Cold Cranking Simulator) viscosity). For this reason, when formulatingmultigrade lubricating oils, other additives belonging to other chemicalclasses have been preferred over polyisobutylene-based additives.

The applicant has surprisingly discovered that radial polymerscontaining a core made up of a calixarene of the general formula (I) towhich are linked a number P of specific hydrogenated linear polymersegments have excellent characteristics with regard to thickeningcapacity, mechanical shear stability, thermo-oxidative stability andlow-temperature behaviour and are therefore capable of overcoming thedisadvantages of known prior art polymers used as additives inlubricating oils.

The present invention therefore relates to hydrogenated polymers with aradial structure having a core made up of calixarenes of the generalformula (I), to the core of which is linked a number P of hydrogenatedlinear polymer segments selected from:

-   -   hydrogenated homopolymers or copolymers of conjugated dienes; or    -   hydrogenated copolymers of said conjugated dienes and        monoalkenyl arenes, and    -   mixtures thereof

The term “hydrogenated” refers to the selective hydrogenation ofolefinic unsaturations, largely leaving the aromatic unsaturationsunchanged.

The present invention also provides a synthesis method for thehydrogenated polymers with a radial structure described and claimed inthe present text.

The radial polymers provided by the present invention have certaincharacteristics, such as thickening capacity, mechanical shearstability, thermo-oxidative stability, reduced tendency to form depositsand low-temperature behaviour, which make them highly suitable for useas additives capable of modifying the viscosity index of lubricatingoils. In particular said polymers, made up of a calixarene core to whichare linked hydrogenated polydiene segments and/or hydrogenatedcopolymers of conjugated dienes and monoalkenyl arenes, are capable ofimparting rheological characteristics, mechanical shear stability,oxidative stability and resistance to the formation of deposits whichare superior to those known in the prior art.

DETAILED DESCRIPTION

The present invention therefore provides hydrogenated polymers with aradial structure having a core made up of calixarenes of the generalformula (I), to the core of which is linked a number P of hydrogenatedlinear polymer segments selected from:

-   -   hydrogenated homopolymers or copolymers of conjugated dienes; or    -   hydrogenated copolymers of said conjugated dienes and        monoalkenyl arenes, and    -   mixtures thereof

Said linear polymer segments are preferably hydrogenated homopolymers orcopolymers of conjugated dienes selected from butadiene, isoprene,1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 3-butyl-1,3-octadiene,1-phenyl-1,3-butadiene and 1,3-hexadiene. The most preferred conjugateddienes are butadiene and isoprene.

Said linear polymer segments are preferably hydrogenated copolymers ofconjugated dienes selected from butadiene, isoprene, 1,3-pentadiene,2,3-dimethyl-1,3-butadiene, 3-butyl-1,3-octadiene,1-phenyl-1,3-butadiene and 1,3-hexadiene, and of monoalkenyl arenes, thelatter selected from styrene, ortho-methylstyrene, para-methylstyrene,meta-methylstyrene, tert-butylstyrene and monovinylnaphthalene. Styreneis the preferred monoalkenyl arene. Preferred hydrogenated copolymers ofconjugated dienes and monoalkenyl arenes are hydrogenatedbutadiene-styrene and isoprene-styrene copolymers.

Preferred polymer segments are hydrogenated copolymers of butadiene andstyrene or hydrogenated copolymers of isoprene and styrene, with thehydrogenated copolymer of butadiene and styrene being still morepreferred.

Calixarenes are well known cyclic compounds derived from thecondensation of p-substituted phenols and formaldehyde. Ring extensionin calixarenes is conventionally indicated in the nomenclature thereofby designating such products as calix[n]arenes, in which with n denotesthe number of units present in the cyclic product.

The calixarenes of the invention are represented by the formula (I)

in which:

-   -   R₁, R₂, R₃ and R₄ are independently selected from hydrogen; a        group containing carbon and hydrogen; a group also containing        heteroatoms in addition to carbon and hydrogen; a group also        containing silicon in addition to carbon, hydrogen and        heteroatoms;    -   one of the two substituents R₅ and R₆ is hydrogen, while the        other may be hydrogen or alkyl, with a number of carbon atoms        between 1 and 6, preferably methyl and ethyl;    -   n is an integer in the range between 4 and 16, preferably        between 6 and 12 and more preferably 8.

In the text, heteroatoms are taken to mean atoms of oxygen, nitrogen,phosphorus, sulfur and halogens.

The number P of linear hydrogenated segments is between 4 and 72,preferably between 16 and 48.

More preferably, P=j*n, where j is the number of polymer segments whicheach phenolic unit can link and is an integer between 1 and 6.

Preferably, R₁ and R₂ may be selected from:

-   -   an alkyl having a number of carbon atoms between 1 and 24,        preferably between 2 and 12; or    -   a group also containing heteroatoms in addition to carbon and        hydrogen and having a number of carbon atoms between 1 and 16;        in this case, preferred heteroatoms are oxygen and halogen; or    -   a group also containing silicon in addition to carbon, hydrogen        and heteroatoms, in which the number of carbon atoms varies        between 5 and 21; preferred among these groups are        alkoxyalkylsilane and haloalkylsilane groups with a number of        carbon atoms between 5 and 21; or    -   an unsaturated hydrocarbon group, with or without heteroatoms,        having a number of carbon atoms between 2 and 16, preferably a        group of the vinyl, allyl or acryloyl type, more preferably of        the vinyl type.

R₃, R₄, R₅ and R₆ are preferably simultaneously hydrogen.

R₁ may more preferably be selected from:

-   -   a group of the formula (II) containing a halogen:

in which X is halogen, preferably selected from Cl, Br and I; R₇ is analkylene or alkenyl group with a number of carbon atoms between 1 and12, preferably between 1 and 6, or arylalkylene with a number of carbonatoms between 7 and 18; R₈ and R₉ are hydrogen or an alkyl or alkenylgroup with a number of carbon atoms between 1 and 12, hydrogen beingpreferred;

-   -   a group of the formula (III) containing an ester type        functionality:

in which R₁₀ is an alkylene or alkenyl group with a number of carbonatoms between 1 and 12, preferably between 1 and 6, or arylalkylene witha number of carbon atoms between 7 and 18; R₁₁ is an alkyl group with anumber of carbon atoms between 1 and 6, preferably methyl and ethyl;

-   -   a group of the formula (IV) containing functionality of the        ketone or aldehyde type:

where R₁₂ is an alkylene or alkenyl group with a number of carbon atomsbetween 1 and 12, preferably between 1 and 6, or arylalkylene with anumber of carbon atoms between 7 and 18; R₁₃ is hydrogen or an alkyl oralkenyl group with a number of carbon atoms between 1 and 12, preferablybetween 1 and 6, or arylalkyl with a number of carbon atoms between 7and 18;

-   -   a group of the formula (V):

where R₁₄ is an alkylene or alkenyl group with a number of carbon atomsbetween 1 and 12, preferably between 1 and 6, or arylalkylene with anumber of carbon atoms between 7 and 18, R₁₅, R₁₆, R₁₇, areindependently an alkyl group with a number of carbon atoms between 1 and8, preferably methyl and ethyl.

R₁ may still more preferably be selected from:

R₁ is still more preferably selected from:

R₂ is more preferably selected from:

-   -   an alkyl having a number of carbon atoms between 1 and 12,        preferably —C(CH₃)₃, —C(CH₃)₂CH₂C(CH₃)₃;    -   a haloalkyl having a number of carbon atoms between 1 and 8,        preferably the group —CH₂Cl;    -   an alkoxycarbonyl having a number of carbon atoms between 2 and        6, preferably the groups —COOCHH₃ and —COOC₂H₅;    -   a group with the formula (V) in which R₁₄, R₁₅, R₁₆ and R₁₇ have        the meanings mentioned above;    -   an alkoxybenzoate group with the formula (VI):

in which R₁₈ is an alkylene group with a number of carbon atoms between1 and 6, preferably methylene and R₁₉ is an alkyl group with a number ofcarbon atoms between 1 and 6, preferably methyl and ethyl.

R₂ is still more preferably selected from:

—C(CH₃)₃; —CH₂Cl; —COOCH₃; —CH₂CH₂CH₂Si(OCH₂CH₃)₃.

Preferred hydrogenated radial polymers have a core made up ofcalixarenes of the formula (I) in which:

-   -   R₁, R₂, R₃ and R₄ are independently selected from hydrogen; a        group containing carbon and hydrogen; a group also containing        heteroatoms in addition to carbon and hydrogen; a group also        containing silicon in addition to carbon, hydrogen and        heteroatoms;    -   one of the two substituents R₅ and R₆ is hydrogen, while the        other may be hydrogen or alkyl, with a number of carbon atoms        between 1 and 6, preferably methyl and ethyl;    -   n is an integer in the range between 4 and 16, preferably        between 6 and 12 and more preferably 8,

and the hydrogenated linear polymer segments are hydrogenated copolymersof butadiene and styrene, or of isoprene and styrene, or hydrogenatedhomopolymers or hydrogenated copolymers of butadiene and isoprene.

Preferred hydrogenated radial polymers have a core made up ofcalixarenes of the formula (I) in which:

-   -   R₁, R₂ are independently selected from hydrogen; a group        containing carbon and hydrogen; a group also containing        heteroatoms in addition to carbon and hydrogen; a group also        containing silicon in addition to carbon, hydrogen and        heteroatoms;    -   R₃, R₄, R₅ and R₆ are simultaneously hydrogen;    -   n is an integer in the range between 4 and 16, preferably        between 6 and 12 and more preferably 8,

and the hydrogenated linear polymer segments are hydrogenated copolymersof butadiene and styrene, or of isoprene and styrene.

More preferred hydrogenated radial polymers have a core made up ofcalixarenes of the formula (I) in which:

-   -   R₁ is selected from substituents of the formula (II),        (Ill), (IV) and (V),    -   R₂ is selected from:        -   an alkyl having a number of carbon atoms between 1 and 12,            preferably —C(CH₃)₃, —C(CH₃)₂CH₂C(CH₃)₃;        -   a haloalkyl having a number of carbon atoms between 1 and 8,            preferably the group —CH₂Cl;        -   an alkoxycarbonyl having a number of carbon atoms between 2            and 6, preferably the groups —COOCH₃ and —COOCH₂H₅;        -   an alkylenetrialkoxysilane group with the formula (V) in            which R₁₄, R₁₅, R₁₆ and R₁₇ have the meanings mentioned            above;        -   an alkoxybenzoate group with the formula (VI);    -   R₃, R₄, R₅ and R₆ are simultaneously hydrogen;    -   n is an integer in the range between 4 and 16, preferably        between 6 and 12 and more preferably 8,

and the hydrogenated linear polymer segments are hydrogenated copolymersof butadiene and styrene, or of isoprene and styrene.

The radial polymers still more preferably have a core made up ofcalixarenes of the formula (I) in which:

-   -   R₁ is selected from:

-   -   R₂ is selected from: —C(CH₃)₃; —CH₂Cl; —COOCH₃;        —CH₂CH₂CH₂Si(OCH₂CH₃)₃;    -   R₃, R₄, R₅ and R₆ are simultaneously hydrogen;    -   n is an integer in the range between 4 and 16, preferably        between 6 and 12 and more preferably 8,

and the hydrogenated linear polymer segments are hydrogenated copolymersof butadiene and styrene, or of isoprene and styrene.

The radial polymers more preferably have a core made up of calixarenesof the formula (I) selected from:5,11,17,23,29,35,41,47-octa-chloromethyl-49,50,51,52,53,54,55,56-octa-hexyloxy-calix[8]arene;5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-[4-(methoxycarbonyl)-benzyloxy]calix[8]arene;5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-(3-triethoxysilylpropoxy)calix[8]arene;5,11,17,23,29,35,41,47-octa-methoxycarbonyl-49,50,51,52,53,54,55,56-octa[4-(methoxycarbonyl)-benzyloxy]calix[8]arene;5,11,17,23,29,35,41,47-octa-(3-triethoxysilylpropyl)-49,50,51,52,53,54,55,56-octa-(3-triethoxysilylpropoxy)calix[8]arene;and have hydrogenated polymer segments selected from hydrogenatedcopolymers of butadiene and styrene, or isoprene and styrene.

The radial polymers more preferably have a core made up of calixarenesof the formula (I) selected from:5,11,17,23,29,35,41,47-octa-chloromethyl-49,50,51,52,53,54,55,56-octa-hexyloxy-calix[8]arene;5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-[4-(methoxycarbonyl)-benzyloxy]calix[8]arene;5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-(3-triethoxysilyl-propoxy)calix[8]arene;5,11,17,23,29,35,41,47-octa-methoxycarbonyl-49,50,51,52,53,54,55,56-octa[4-(methoxycarbonyl)-benzyloxy]calix[8]arene;5,11,17,23,29,35,41,47-octa-(3-triethoxysilylpropyl)-49,50,51,52,53,54,55,56-octa-(3-triethoxysilylpropoxy)calix[8]arene;and have hydrogenated polymer segments selected from hydrogenatedhomopolymers of butadiene.

Method for Synthesising the Radial Polymers Described and Claimed in thePresent Patent Application.

The present invention further provides a synthesis method for the radialpolymers described and claimed in the present text, which methodcomprises the following stages:

-   i. synthesising a calixarene of the general formula (I);-   ii. preparing the linear polymer segments by anionic polymerisation    in solution of one or more conjugated dienes, or by copolymerisation    of one or more conjugated dienes and a monoalkenyl arene, in the    presence of an ionic initiator to form a living anionic polymer;-   iii. reacting the living anionic polymer obtained in (ii) with the    calixarene synthesised in (i) to form a polymer with a radial    structure; and-   iv. reacting, by selective hydrogenation, the olefinic unsaturations    present in the radial polymer obtained in (iii) to obtain a    hydrogenated radial polymer.

The living anionic polymers produced in stage (ii) are the precursors ofthe hydrogenated linear polymer chains which extend radially outwardsfrom the core of the calixarene. In a preferred embodiment of thepresent invention, the substituents R₁ and R₂ of the calixarene areselected such that, for each of the units n of the calix[n]arene, atleast one or both of the substituents have a functionality capable ofreacting with the living anionic polymer, so giving rise to the radialpolymer.

The number of hydrogenated linear polymer segments P in the final radialpolymer thus depends on the number n of units of the calix[n]arene, onthe number of groups R₁ and R₂ reactive towards the living anionicpolymer, on the number of living anionic polymer units which each of thegroups R₁ and R₂ is capable of linking and on the yield of the couplingreaction between the living anionic polymers and the calixarenes.

The groups R₁ and R₂ must not contain acidic hydrogens capable ofreacting with the living anionic polymer, so removing the latter fromthe coupling reactions with the calixarene which lead to the formationof the radial polymers.

Groups R₁ and R₂ containing an ester type functionality are capable oflinking two living anionic polymer units; this is because the reactionwith a first living anionic polymer unit proceeds with elimination ofthe alkoxide and formation of a ketone species which is in turn capableof linking a second living anionic polymer unit by means of an additionreaction, so forming the radial polymer.

Groups R₁ and R₂ containing an aldehyde or ketone type functionality arecapable of linking just one living anionic polymer unit by means of anaddition reaction.

Groups R₁ and R₂ containing a halogenated alkyl functionality arecapable of linking one living anionic polymer unit by means of asubstitution reaction.

Alkyltrialkoxysilane groups, on the other hand, are capable of linkingthree living anionic polymer units with elimination of the correspondingalkoxides.

Groups R₁ or R₂ which comprise an olefinic unsaturation, preferably ofthe vinyl, allyl or acryloyl type, can link one living anionic polymerunit by means of an addition reaction.

Stage (i): Synthesis of Calixarene Cores

The synthesis of calixarenes of the formula (I) where R₁=R₃=R₄=H is wellknown in the prior art and is typically performed by means ofcondensation between phenols which are p-substituted, preferentiallywith alkyl groups, and formaldehyde at elevated temperature, asindicated in scheme 1 below:

The catalysts used are usually metal hydroxides, preferentially ofalkali or alkaline earth metals, as indicated, for example, in Gutsche,C. D. et al. Org. Synth. 1990, 68, 234-246. Lewis acids have alsorecently been used with good yields with the assistance of microwaveirradiation, as indicated in Bew, S. P. et al. Chem. Commun. 2007,975-977; Bew, S. P. et al. J. Org. Chem. 2011, 76, 7076-7083. Typically,the size of the macrocycle may conveniently be adjusted by changing thebase cation, the solvent and the heating temperature. In the case ofsome phenols, typically p-tert-butylphenol, consolidated experimentalprocedures (for example in Gutsche, C. D. et al. Org. Synth. 1990, 68,234-246 and Gutsche, C. D. Org. Prep. Proced. Int. 1992, 25, 137-139)allow synthesis to be directed with excellent yields (60-90%) to theproducts of the formula (I) with R₁=R₃=R₄=H, R₂=tert-C₄H₉ and bearingn=4, 5, 6 or 8. Typically, in order to synthesise thep-tert-butylcalix[8]arene derivative of the formula (I) with R₁=R₃=R₄=H,R₂=tert-C₄H₉ and n=8, the p-tert-butylphenol (1) indicated in scheme 1and paraformaldehyde are reacted with NaOH in xylene at refluxtemperature. The quantities of paraformaldehyde and NaOH used arerespectively 1.7 equivalents and 0.03 equivalents per equivalent ofp-tert-butylphenol. Following removal of water from the distillationhead, the desired product may be isolated by filtration after 4 hours'reaction as a cyclic octameric derivative (1_(n)) with n=8, indicated inscheme 1.

For the purposes of the present invention, calixarenes with freehydroxyl groups, such as for example (1_(n)), are functionalised at thelower rim (R₁ of the formula (I)) and/or at the upper rim (R₂ of theformula (I)) with groups containing functionalities capable of linkingliving anionic polymer units. Functionalities of the ketone, aldehydeand haloalkyl type are capable of linking at most one living anionicpolymer unit; functionalities of the ester type are capable of linkingat most two living anionic polymer units; alkyltrialkoxysilane groupsare capable of linking at most three living anionic polymer units.

The general methods for preparing the preferred calixarenes of theinvention are indicated below by way of example.

Stage (i) (Synthesis of Calixarene Cores): Synthesis of CalixareneDerivatives to which One Polymer Segment May be Added for Each PhenolicCore.

Calixarene derivatives containing chloromethyl groups on the upper rimof each phenolic unit were prepared by following a procedure comprisingthe reactions indicated in scheme 2 below.

The tert-butyl groups may readily be removed from thep-tert-butylcalix[n]arenes by using AlCl₃ in toluene, as is well knownin the literature (Gutsche, C. D. et al. J. Org. Chem., 1985, 50,5802-5806).

Treating p-tert-butylcalix[8]arene (2) with AlCl₃ (0.25 equiv. for eachphenolic core) for 2 hours at 60° C. under an inert atmosphere yieldsthe derivative (3), so enabling functionalisation of the upper rim (paraposition relative to the phenolic oxygen) of the calixarenes.

Alkylating (3) with 1-bromohexane (5 equiv. for each phenolic core) andNaH (10 equiv. for each phenolic core) in anhydrous DMF (Perret et al.New J. Chem., 2007, 31, 893-900) allows isolation of the derivative (4)which, according to the literature (Casnati, A. et al. Tetrahedron 1989,45, 2177-2182), reacts in CHCl₃ with chloromethyl octyl ether (10 equiv.for each phenolic core) and tin tetrachloride (4 equiv. for eachphenolic core), so leading to the formation of compound (5) (90% yield).

Stage (i) (Synthesis of Calixarene Cores): Synthesis of CalixareneDerivatives to which Two Polymer Segments May be Added for Each PhenolicCore.

Calixarene derivatives with ester type functionality are prepared byalkylating calixarene (2) on the phenolic oxygens by reaction with haloesters, preferably with 4-(bromomethyl)methyl benzoate and potassiumcarbonate in acetone at reflux temperature according to scheme 3 below.The quantity of 4-(bromomethyl)methyl benzoate used is between 1 and 1.5equivalents per equivalent of p-tert-butylphenol and that of potassiumcarbonates is between 1.1 and 2 equivalents per equivalent ofp-tert-butylphenol. The octafunctionalised product (6) obtainedaccording to scheme 3, is isolated and, after appropriate dehydration,used in the reaction with living anionic polymers.

Stage (i) (Synthesis of Calixarene Cores): Synthesis of CalixareneDerivatives to which Three Polymer Segments May be Added for EachPhenolic Core.

An alternative product to be used as a core in the reactions with theliving anionic polymer is derivative (8), obtained according to scheme 4indicated below. In order to obtain said product, thep-tert-butylcalix[8]arene (2), of the formula (I), with R₁=R₃=R₄=H,R₂=tert-C₄H₉ and n=8, is reacted under phase-transfer conditions withKOH (1.5 equiv. for each phenolic core), allyl bromide (3 equiv. foreach phenolic core) in a 1:1 mixture of water and dichloromethane and inthe presence of polyethylene glycol with an average molecular weight of600 (PEG 600) according to the literature (Wang et al. SyntheticCommunications 1999, 29, 3711-3718). After isolation, the resultantocta-allyl ether of p-tert-butylcalix[8]arene (7) is reacted withtriethoxysilane (1.5 equiv. for each phenolic core) andhexachloroplatinic acid hexahydrate (catalytic quantity) in toluene atreflux temperature for 16 hours. After filtration and removal of thetoluene and excess triethoxysilane, the derivative (8) is isolated.

Stage (i) (Synthesis of Calixarene Cores): Synthesis of Derivatives towhich 4 Polymer Segments (2 to the Upper Rim and 2 to the Lower Rim) Maybe Added for Each Phenolic Core.

Calixarene derivatives containing ester groups on both the lower and theupper rim of each phenolic unit were prepared by following a procedurecomprising the reactions indicated in scheme 5 below.

Treating p-tert-butylcalix[8]arene with AlCl₃ (0.25 equiv. for eachphenolic core) for 2 hours at 60° C. under an inert atmosphere yieldsthe derivative (3) which, as a result of subsequent treatment withhexamethylenetetramine (HMTA, 11 equiv. for each phenolic core) intrifluoroacetic acid (8 equiv. for each phenolic core) at 140° C. for 5hours, leads to the formyl group being introduced and compound (9) beingobtained, as stated in the literature (Pasquale, S. et al. Nat. Commun.,2012, 3, 785). Following subsequent oxidation of compound 9 with NaClO₂(4 equiv. for each phenolic core) and NaH₂PO₄ (0.15 equiv. for eachphenolic core), the octaacid (10) is obtained which, once methylatedunder conventional Fischer esterification conditions, yields theoctaester (11). Alkylating the latter with 4-bromomethylmethyl benzoateand K₂CO₃ in acetone at reflux temperature allows isolation of thederivative (12) which has ester groups on both the upper and the lowerrim and allows the insertion of 4 polymer chains per phenolic core ofthe macrocycle.

Stage (I) (Synthesis of Calixarene Cores): Synthesis of Derivatives towhich 6 Polymer Segments (3 to the Upper Rim and 3 to the Lower Rim) Maybe Added for Each Phenolic Core.

As shown in scheme 6 below, compound (13) is obtained starting fromderivative (3) and inserting the allyl groups on the lower rim followingalkylation under phase-transfer conditions (PEG 600), with allyl bromide(3 equiv. for each phenolic core), in the presence of KOH (1.5 equiv.for each phenolic core) and in dichloromethane/water as solvent.

After treatment with N,N-diethylaniline (12 equiv. for each phenoliccore), derivative (13) gives rise to derivative (14) following Friestransposition, which is also well known on calixarenes (Gutsche, C. D.et al. J. Org. Chem., 1985, 50, 5802-5806). Compound (14), after beingreacted under the above-described phase-transfer conditions with KOH andallyl bromide, allows isolation of the hexadecaallyl derivative (15).Subsequent treatment with hexachloroplatinic acid (catalytic quantities)and triethoxysilane (1.5 equiv. for each allyl residue) in toluene atreflux temperature for 16 hours yields the derivative (16).

Stage (ii): Preparation of Living Anionic Polymer Segments

The living polymers of the present invention may be prepared by means ofwell known methods of anionic polymerisation in solution of one or moreconjugated dienes, or copolymerisation of one or more conjugated dienesand one or more monoalkenyl arenes in the presence of an anionicpolymerisation initiator, such as, for example, an alkalimetal-hydrocarbon compound. Examples of initiators include organiclithium compounds, such as alkyllithium compounds, in particularmethyllithium, n-butyllithium, sec-butyllithium, cycloalkyllithiumcompounds, in particular cyclohexyllithium and aryllithium compounds, inparticular phenyllithium, 1-methylstyryllithium, p-tolyllithium,naphthyl-lithium and 1,1-diphenyl-3-methylpentyllithium. Other examplesof initiators include sodium naphthalene,1,4-disodio-1,1,4,4-tetraphenylbutane, diphenylmethylpotassium anddiphenylmethylsodium.

Examples of conjugated dienes which are suitable for use in thepreparation of the living polymer include butadiene; isoprene;1,3-pentadiene; 2,3-dimethyl-1,3-butadiene; 3-butyl-1,3-octadiene;1-phenyl-1,3-butadiene; 1,3-hexadiene. Butadiene and isoprene are thepreferred dienes.

The concentration of the initiator used is determined by the desiredmolecular weight of the living polymer.

Apart from being derived from one or more conjugated dienes, the livingpolymer may also be derived from one or more monoalkenyl arenes.Examples of monoalkenyl arenes include styrene, ortho-methylstyrene,para-methylstyrene, meta-methylstyrene, tert-butylstyrene andmonovinylnaphthalene. Styrene is the preferred monoalkenyl arene. If themonoalkenyl arenes are used in the preparation of the living polymer,the quantity thereof is between 2% by weight and 50% by weight relativeto the total weight of the sum of the dienes and the monoalkenyl arenes.

The living polymers may be living homopolymers, living copolymers,living terpolymers or living quaterpolymers.

The living homopolymers may be represented by the formula A-M, in whichM is for example lithium and A is for example polybutadiene orpolyisoprene.

The living copolymers may be represented by the formula A-B-M in which Mis for example lithium and A-B may be a “random” copolymer, or a blockcopolymer, or alternatively a “tapered” copolymer. In the case of randomcopolymers, the two monomers follow one another along the chain withoutany order. Said type of polymers may be obtained by using polymerisationmethods known in the prior art. In the case of block copolymers, asequence of greater or lesser length formed by monomer A is followed byanother formed by monomer B.

Such types of polymers are prepared by successive additions of the twomonomers to the reaction. For example, in the case of styrene-butadienecopolymers, polymerisation of butadiene results in a living polymerwhich, following subsequent addition of styrene, forms apolybutadiene-polystyrene-M block copolymer. Conversely, if the styreneis polymerised first and the butadiene is added subsequently, apolystyrene-polybutadiene-M block copolymer is formed. Using thisapproach, it is possible to obtain a living polymer with the desirednumber of blocks and the desired sequence of monomer blocks.

By combining the above-stated approaches it is possible to form a livingcopolymer with a partially “random” and partially block structure.

“Tapered” living copolymers, which are formed when a mixture of twomonomers of differing reactivities is polymerised, are characterised bya polymer chain which contains the two relatively pure monomers at thetwo ends. Moving from one end to the other of the polymer chain, thereis a reduction in content of the first monomer and an increase in thecontent of the second monomer.

Preferred living polymers are those arising from the copolymerisation ofa conjugated diene, preferably butadiene or isoprene, with a monoalkenylarene, preferably styrene, characterised by a monoalkenyl arene contentbetween 3% by weight and 30% by weight relative to the total weight ofthe copolymer, and a diene content between 97% by weight and 70% byweight relative to the total weight of the copolymer. Still morepreferred are those living polymers arising from the copolymerisation ofbutadiene and styrene characterised by a styrene content between 5% byweight and 25% by weight relative to the total weight of the copolymerand a butadiene content between 95% by weight and 75% by weight relativeto the total weight of the copolymer. The preference for livingcopolymers derived from the copolymerisation of butadiene and styrene isdictated by costs, commercial availability and ease of use of the rawmaterials.

In a further preferred embodiment of the present invention,copolymerisation is carried out in the presence of modifying agents, inparticular ethers and/or amines, the primary purpose of which is topromote polymerisation, to randomise copolymerisation and to modify themicrostructure of the polydiene segment. In particular, as indicated ininternational patent application WO 2012/055802, when butadiene is used,the modifying agents have the purpose of increasing the 1,2 linkagecontent of the conjugated diene relative to the 1,4 linkage content.This is because it is preferred for the polymer derived from 1,2 linkageof the butadiene to make up more than 50% of the total polybutadiene.Butadiene 1,2 linkage contents of less than 50% result in the formation,after hydrogenation of the olefinic unsaturations, of a crystallinepolymer which is not desired because it impairs the low-temperaturebehaviour of the star polymer when used as an additive for modifying theviscosity index of lubricating oils. This is because crystallinity ofthe final polymer has a negative impact on the pour point and MRV(mini-rotary viscometer) viscosity of the lubricating oil. Examples ofmodifying agents include diethylene glycol dimethyl ether, diethyleneglycol diethyl ether, diethylene glycol dibutyl ether, triethyleneglycol dimethyl ether, triethylene glycol diethyl ether,tetrahydrofuran, 2-methoxyethyltetrahydrofuran,2-methoxymethyltetrahydrofuran and dioxane.

The copolymerisation process is carried out in the presence of at leastone inert solvent. Examples of solvents which may be used includealiphatic hydrocarbons, such as for example isobutanol, pentane,cyclopentane, hexane, cyclohexane, heptane, methylcyclohexane, octaneand 2-ethylhexane; aromatic hydrocarbons, such as for example benzene,toluene, ethylbenzene and xylene; ethers, such as for exampletetrahydrofuran, diglyme and tetraglyme.

The temperature at which copolymerisation may be carried out is between0° C. and 150° C., preferably between 20° C. and 100° C.

The copolymerisation process is carried out in the absence of oxygen andmoisture, preferably under an inert atmosphere, at an absolute pressurebetween 0.5 and 10 atm, preferably a pressure between 1 and 5 atm.

The weight-average molecular weight (M_(W)), determined by GPC, of theliving polymers prepared in stage (ii) of the process for preparing thestar polymers is between 10000 and 200000, preferably between 14000 and100000.

Stage (iii): Coupling Reaction of Living Anionic Polymers withCalixarenes

Once produced, the living polymers are reacted in reaction stage (iii)of the method for preparing the radial polymers described and claimed inthe present text, with the calixarenes produced in reaction stage (i).The calixarene is added to the living polymer once polymerisation of themonomers in stage (ii) is complete.

The quantity of calixarene in mol which is added depends on the numberof linear polymer segments which the calixarene can link. The quantityof calixarene is between 0.8/P mol and 1.2/P mol per mol of livingpolymer, more preferably between 0.9/P mol and 1.1/P mol.

Reaction stage (iii) is carried out in the presence of at least oneinert solvent. Examples of solvents which may be used include aliphatichydrocarbons, such as for example isobutanol, pentane, cyclopentane,hexane, cyclohexane, heptane, methylcyclohexane, octane and2-ethylhexane; aromatic hydrocarbons, such as for example benzene,toluene, ethylbenzene and xylene; ethers, such as for exampletetrahydrofuran, diglyme and tetraglyme.

Reaction stage (iii) is preferably carried out in the same solvent usedin reaction stage (ii), at a temperature between 0° C. and 150° C.,preferably between 20° C. and 100° C. The reaction is carried out in theabsence of oxygen and moisture, preferably under an inert atmosphere, atatmospheric pressure or alternatively at an absolute pressure between0.5 and 10 atm, preferably between 1 and 5 atm.

The yield of the coupling reaction between the living anionic polymersand the calixarenes is greater than 50%, preferably greater than 80%.

If the polymer with a radial structure of reaction stage (iii) is inanionic form, it may be deactivated using known procedures by additionof a compound capable of reacting with the anion. Examples ofdeactivators include compounds comprising active hydrogen such as waterand alcohols.

The radial polymer prepared in reaction stage (iii) is characterised byhaving a central core made up of the calixarene to which are radiallylinked a number P of polymer segments which extend outwards from thecore. The larger is the number of polymer segments linked to thecalixarene, the better is the thickening power. At identical thickeningpower, the larger is the number of polymer segments, the better ismechanical shear stability because it is possible in this manner to havea high molecular weight radial polymer without there being any need tohave excessively long polymer segments.

Stage (iv): Hydrogenation of the Star Polymer

The star polymer produced in reaction stage (iii) is hydrogenated insuch a manner that the degree of hydrogenation of the initially presentolefinic unsaturations is greater than 85%, preferably greater than 94%.

The hydrogenation catalyst and hydrogenation conditions used make itpossible for the quantity of aromatic unsaturations which arehydrogenated in the calixarene and in the monoalkenyl arene, when used,to be less than 5%, more preferably less than 2%. Hydrogenation may becarried out using known catalysts containing either noble metals ornon-noble metals. Preference is given to catalysts based on non-noblemetals and in particular the catalysts containing titanium mentioned inEuropean patent EP 1721910 are preferred.

The hydrogenated star polymer is then recovered from the solution bymeans of a series of operations including removal of the solvent anddrying.

The weight-average molecular weight (M_(W)) of each of the hydrogenatedlinear polymer segments which make up the hydrogenated star polymer isbetween 10000 and 200000, preferably between 14000 and 100000.

The weight-average molecular weight (M_(W)) of the hydrogenated starpolymers provided by the present invention is between 100000 and2000000, preferably between 200000 and 1000000.

Average molecular weights are determined by gel permeationchromatography (GPC) with a UV detector using polystyrene as calibrationstandard.

Use of the Hydrogenated Star Polymers in Lubricant Formulations

The hydrogenated star polymers provided by the present invention may beused as viscosity index-improver additives in lubricant compositions.

For formulation of the lubricants, said hydrogenated star polymers maybe added as such in the form of solids, or they may be in solution,preferably in solution with a lubricant base oil.

The base oils used as solvents for dissolving the hydrogenated starpolymers are selected from base oils of a mineral, synthetic, vegetableor animal origin and mixtures thereof.

Oils of mineral origin are derived from known petroleum refiningprocesses, such as for example distillation, deparaffination,deasphaltation, dearomatisation and hydrogenation. Oils of syntheticorigin include hydrocarbons oils, such as for example polymerised andhydrogenated terminal or internal olefins; alkylbenzenes; polyphenyls;alkylated diphenyl ethers; polyalkylene glycols and derivatives in whichthe terminal hydroxyl groups have been modified, for example byesterification or etherification.

Another class of synthetic lubricating oils comprises esters ofsynthetic or animal or vegetable-derived carboxylic acids with a varietyof alcohols or polyols.

A further class of synthetic lubricating oils comprises carbonic acidesters with a variety of alcohols and polyols.

Typical examples of vegetable oils are soy, palm or castor oil, whileexamples of oils of origin animal are tallow oil, lard oil or whale oil.

Another way of classifying base oils is that set out by the AmericanPetroleum Institute (API) in the publication “Engine Oil Licensing andCertification System” (API EOLCS, 1507—Industry Services Department,Fourteenth Edition, December 1996, Addendum 1, December 1998). Base oilsare subdivided into five groups as a function of their physicochemicaland compositional characteristics.

According to this classification, the base oils used for dissolving thestar polymers may belong to any of the above-stated API groups,preferably to API groups I, II, III and IV and still more preferably toAPI groups I, II and III.

The viscosity index-improver additives, obtained by dissolving thehydrogenated star polymers in base oils, have a polymer concentration,expressed as a percentage by weight of the polymer in the solution madeup of the polymer and base oil, between 1 and 30, preferably between 5and 25.

The present invention further provides lubricant compositions, alsodesignated lubricant formulations, containing one or more of one of thelubricant base oils previously described and one or more of thehydrogenated star polymers described and claimed in the present patentapplication, used at a total concentration, expressed as a percentage byweight of the polymer in the finished lubricant oil, between 0.1 and 5,preferably between 0.3 and 2.

Where solutions of the star polymers in base oils are used to formulatelubricants, the lubricant compositions provided by the invention containone or more of said solutions at a total concentration, expressed as apercentage by weight of the solution in the finished lubricant oil,between 0.5 and 50, preferably between 3.5 and 30, more preferablybetween 5 and 18.

Such lubricant compositions, used for example as automotive oils, maycontain, in addition to the above-stated additives, one or moreadditives selected from detergent additives, dispersant additives,antioxidant additives, friction-modifier additives, antiwear and extremepressure (EP) additives, corrosion inhibitors, pour point-depressantadditives, foam inhibitors, emulsifiers and others.

Some illustrative, non-limiting examples of the invention are providedbelow for the purpose of elucidating the present invention.

Example 1: Synthesis of the Calixarene of the Formula (5)

A calix[8]arene derivative which may be used according to a preferredembodiment of the present invention for synthesising star polymers is5,11,17,23,29,35,41,47-octa-chloromethyl-49,50,51,52,53,54,55,56-octa-hexyloxy-calix[8]arenewhich may be represented by the structure (5):

111.2 g (0.72 mol) of tert-butylphenol (1), 27 g (1.2 mol) ofp-formaldehyde, 1.6 mL (0.016 mol) of 10 N NaOH and 600 mL of xylene areintroduced under an inert atmosphere into a 1 L, 3-necked glass flaskequipped with a mechanical paddle stirrer and “Dean and Stark” collectorfitted with a condenser. The mixture is adjusted to reflux while beingstirred and maintained under such conditions for 4 hours, during whichthe water of reaction is collected in the “Dean and Stark” collector.

After cooling to room temperature, the mixture is filtered and the solidproduct is washed in succession with toluene, ether, acetone and water.Once dried, the product is recrystallised from chloroform. 65.8 g (yield70.4%) of solid white product are recovered.

The purity of the product p-tert-butylcalix[8]arene (2) is verified byESI mass spectrometry, which reveals a single monodisperse signal.

8.25 g (6.36 mmol) of p-tert-butylcalix[8]arene (2), 1.70 g (12.7 mmol)of anhydrous aluminium trichloride, 10 mL of phenol and 100 mL oftoluene are introduced under an inert atmosphere into a 250 mL, 3-neckedglass flask fitted with a mechanical stirrer and condenser. The mixtureis adjusted, while being stirred, to a temperature of 60° C. and keptunder such conditions for 2 hours. 100 mL (100 mmol) of 1N HCl areadded, the mixture is stirred and then transferred into a separatingfunnel, where the solvent is removed under reduced pressure from theseparated organic phase, resulting in a white solid. Once dried, theproduct is recrystallised from chloroform/methanol.

4.10 g (yield 76%) of the product calix[8]arene (3) are obtained.

4.10 g (4.83 mmol) of calix[8]arene (3), 15.46 g (386.4 mmol) of NaH 60%in mineral oil and 50 mL of anhydrous DMF are introduced under an inertatmosphere into a 100 mL 3-necked glass flask fitted with a stirrer,thermometer and condenser. The mixture is left to react at roomtemperature for 30 min under an inert atmosphere.

27.12 mL (193.2 mmol) of 1-bromohexane are subsequently added.

The mixture is adjusted to 70° C. for 24 hours under an inertatmosphere.

After cooling to room temperature, 10 mL (100 mmol) of 1N HCl are added,the mixture is stirred and transferred into in a separating funnel wherethe organic phase is extracted with toluene, separating it from theaqueous phase.

The solvent is removed under reduced pressure, resulting in a whitesolid.

Once dried, the product is recrystallised from methanol.

7.41 g (yield 80%) of the product49,50,51,52,53,54,55,56-octa-hexyloxy-calix[8]arene (4) are obtained.

7.41 g (3.87 mmol) of49,50,51,52,53,54,55,56-octa-hexyloxy-calix[8]arene (4), 54.7 g (306mmol) of chloromethyl octyl ether, and 500 mL of chloroform areintroduced under an inert atmosphere into a 1 L, 3-necked glass flaskfitted with a mechanical paddle stirrer, thermometer and condenser. Themixture is adjusted to −15° C. while being stirred and 14 mL (120 mmol)of tin tetrachloride are added dropwise with stirring under an inertatmosphere.

The mixture is reacted for 1 hour with stirring under an inertatmosphere and at room temperature. 50 mL of distilled water are addeddropwise, the mixture is stirred and the aqueous phase separated in aseparating funnel. The organic phase is washed with distilled water andthe solvent is subsequently removed under reduced pressure. Once dried,the product is recrystallised from heptane. 8.02 g (yield 90%) of theproduct5,11,17,23,29,35,41,47-octa-chloromethyl-49,50,51,52,53,54,55,56-octa-hexyloxy-calix[8]arene(5) are obtained.

Example 2: Preparation of the Hydrogenated Isoprene-Styrene Star Polymerfrom the Calixarene of the Formula (5)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 1.2 g of tetrahydrofuran arethen added. The solution is then thermostated to 40° C. Once saidtemperature has been reached, 0.49 g of n-butyllithium in a cyclohexanesolution (7.65 mmol) are added. After 20 minutes, once styreneconversion is complete, 423 g of isoprene are added. After 30 minutes,once isoprene conversion is complete, 1.83 g (0.956 mmol) of thecalixarene of the formula (5) are added in a tetrahydrofuran solution.The reaction mixture is then maintained at a temperature of 40° C. for 1h.

The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The solution is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h and 30 minutes whilebeing stirred. The solution is then transferred into a tank, hasantioxidants (2.6 g of Irganox 565 and 17 g of Irgafos 168) added and issubsequently transferred into a stripping system in which the solvent isremoved by steam; the resultant granular product is then dried in avacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 1.

Example 3: Synthesis of the Calixarene of the Formula (6)

A calix[8]arene derivative which may be used according to a furtherpreferred embodiment of the present invention for synthesising starpolymers is5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-[4-(methoxy-carbonyl)-benzyloxy]calix[8]arenewhich may be represented by the structure (6):

8.25 g (6.36 mmol) of p-tert-butylcalix[8]arene (2), the synthesis ofwhich is described in Example 1, 16.45 g (71.8 mmol) of4-(bromomethyl)methyl benzoate, 5.14 g (30.9 mmol) of KI, 13.26 g (30.9mmol) of K₂CO₃ and 100 mL of acetone are introduced under an inertatmosphere into a 250 mL 3-necked glass flask fitted with a mechanicalpaddle stirrer, thermometer and condenser. The mixture is adjusted toreflux while being stirred and maintained under such conditions for 48hours.

After cooling to room temperature, 100 mL (100 mmol) of 1N HCl areadded, the mixture is stirred and extracted in a separating funnel withtoluene, separating the organic phase from the aqueous phase. Thesolvent is removed from the organic phase under reduced pressure,resulting in a white solid.

Once dried, the product is recrystallised from methanol.

8.10 g (yield 51.3%) of the product5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa[4-(methoxycarbonyl)-benzyloxy]calix[8]arene(6) are obtained.

Example 4: Preparation of the Hydrogenated Isoprene-Styrene Star Polymerfrom the Calixarene of the Formula (6)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 1.2 g of tetrahydrofuran arethen added. The solution is then thermostated to 40° C. Once saidtemperature has been reached, 0.82 g of n-butyllithium in a cyclohexanesolution (12.80 mmol) are added. After 20 minutes, once styreneconversion is complete, 423 g of isoprene are added. After 30 minutes,once isoprene conversion is complete, 1.99 g (0.800 mmol) of thecalixarene of the formula (6) are added in a tetrahydrofuran solution.The reaction mixture is then maintained at a temperature of 40° C. for45 minutes.

The mixture is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The solution is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h and 30 minutes whilebeing stirred. The solution is then transferred into a tank, hasantioxidants (2.6 g of Irganox 565 and 17.0 g of Irgafos 168) added andis then subsequently transferred into a stripping system in which thesolvent is removed by steam; the resultant granular product is thendried in a vacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 1.

Example 5: Preparation of the Hydrogenated Butadiene-Styrene StarPolymer from the Calixarene of the Formula (6)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 95 g of tetrahydrofuran are thenadded. The solution is then thermostated to 40° C. Once said temperaturehas been reached, 0.82 g of n-butyllithium in a cyclohexane solution(12.80 mmol) are added. After 20 minutes, once styrene conversion iscomplete, 423 g of 1,3-butadiene are added. After 30 minutes, oncebutadiene conversion is complete, 1.99 g (0.800 mmol) of the calixareneof the formula (6) are added in a tetrahydrofuran solution. The reactionmixture is then maintained at a temperature of 40° C. for 45 minutes.The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The mixture is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h while being stirred. Thesolution is then transferred into a tank, has antioxidants (2.6 g ofIrganox 565 and 17.0 g of Irgafos 168) added and is subsequentlytransferred into a stripping system in which the solvent is removed bysteam; the resultant granular product is then dried in a vacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 2.

Example 6: Preparation of the Hydrogenated Star Polybutadiene from theCalixarene of the Formula (6)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 500 g of 1,3-butadiene and 95 g of tetrahydrofuranare then added. The solution is then thermostated to 40° C. Once saidtemperature has been reached, 0.82 g of n-butyllithium in a cyclohexanesolution (12.80 mmol) are added. After 20 minutes, once butadieneconversion is complete, 1.99 g (0.800 mmol) of the calixarene of theformula (6) are added in a tetrahydrofuran solution. The reactionmixture is then maintained at a temperature of 40° C. for 45 minutes.

The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The mixture is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h while being stirred. Thesolution is then transferred into a tank, has antioxidants (2.6 g ofIrganox 565 and 17.0 g of Irgafos 168) added and is subsequentlytransferred into a stripping system in which the solvent is removed bysteam; the resultant granular product is then dried in a vacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 2.

Example 7: Synthesis of the Calixarene of the Formula (8)

A calix[8]arene derivative which may be used according to a furtherpreferred embodiment of the present invention for synthesising starpolymers is5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-(3-triethoxysilyl-propoxy)calix[8]arene,which may be represented by the structure (8):

8.25 g (6.36 mmol) of p-tert-butylcalix[8]arene (2), the synthesis ofwhich is described in Example 1, 13.3 mL (153 mmol) of bromoallyl, 4.3 g(76 mmol) of KOH, 2 mL of PEG 600, 20 mL of distilled water and 20 mL ofdichloromethane are introduced into a 100 mL 3-necked glass flask fittedwith a stirrer, thermometer and condenser. The mixture is kept under aninert atmosphere and at room temperature for 24 hours. 100 mL (100 mmol)of 1N HCl are added, the mixture is stirred and transferred into aseparating funnel where the organic phase is extracted with chloroform,separating it from the aqueous phase. The solvent is removed underreduced pressure, resulting in a white solid.

Once dried, the product is recrystallised from methanol.

5.96 g (yield 58%) of the product5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-allyloxy-calix[8]arene(7) are obtained. 5.96 g (3.69 mmol) of5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-allyloxy-calix[8]arene(7), 8.16 mL (44.28 mmol) of triethoxysilane, 100 mg (0.19 mmol) ofdihydrogen hexachloroplatinate(VI) hexahydrate and 50 mL of toluene areintroduced under an inert atmosphere into a 100 mL 3-necked glass flaskfitted with a stirrer, thermometer and condenser. The mixture isadjusted to reflux while being stirred and maintained under suchconditions for 16 hours.

The mixture is hot filtered and the solvent present in the filtrate isremoved under reduced pressure. Once dried, the product isrecrystallised from heptane.

7.55 g (yield 70%) of the product5,11,17,23,29,35,41,47-octa-tert-butyl-49,50,51,52,53,54,55,56-octa-(3-triethoxysilylpropoxy)calix[8]arene(8) are obtained.

Example 8: Preparation of the Hydrogenated Isoprene-Styrene Star Polymerfrom the Calixarene of the Formula (8)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 1.2 g of tetrahydrofuran arethen added. The solution is then thermostated to 40° C. Once saidtemperature has been reached, 0.82 g of n-butyllithium in a cyclohexanesolution (12.80 mmol) are added. After 20 minutes, once styreneconversion is complete, 423 g of isoprene are added. After 30 minutes,once isoprene conversion is complete, 1.56 g (0.533 mmol) of thecalixarene of the formula (8) are added in a tetrahydrofuran solution.The reaction mixture is then maintained at a temperature of 40° C. for 1h.

The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The mixture is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h and 30 minutes whilebeing stirred. The solution is then transferred into a tank, hasantioxidants (2.6 g of Irganox 565 and 17.0 g of Irgafos 168) added andis subsequently transferred into a stripping system in which the solventis removed by steam; the resultant granular product is then dried in avacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 1.

Example 9: Synthesis of the Calixarene of the Formula (12)

A calix[8]arene derivative which may be used according to a furtherpreferred embodiment of the present invention for synthesising starpolymers is5,11,17,23,29,35,41,47-octa-methoxycarbonyl-49,50,51,52,53,54,55,56-octa-[4-(methoxycarbonyl)benzyloxy]calix[8]arene,which may be represented by the structure (12):

4.10 g (4.83 mmol) of calix[8]arene (3), the synthesis of which isdescribed in Example 1, 60.8 g (443 mmol) of hexamethylenetetramine(HMTA) and 450 mL of trifluoroacetic acid are introduced under an inertatmosphere into a 2 L 3-necked flask fitted with a mechanical paddlestirrer, thermometer and condenser. The mixture is adjusted, while beingstirred, to a temperature of 140° C. and maintained under suchconditions for 5 hours.

500 mL (100 mmol) of 1N HCl and 500 mL of CHCl₃ are added, the mixtureis stirred and the organic phase is separated from the aqueous phase ina separating funnel.

The solvent is removed under reduced pressure and the resultant solid isrecrystallised from dichloromethane.

3.63 g (yield 70%) of the product5,11,17,23,29,35,41,47-octa-formyl-calix[8]arene (9) are obtained as adark yellow solid.

3.63 g (3.38 mmol) of 5,11,17,23,29,35,41,47-octa-formyl-calix[8]arene(9) in 60 mL of DMSO and 50 mL of distilled water are introduced underan inert atmosphere into a 500 mL 3-necked glass flask fitted with amechanical paddle stirrer, thermometer and condenser.

Subsequently, 0.48 g (4.04 mmol) of NaH₂PO₄ and dropwise, over a periodof 3 hours, a solution of 10 g (111 mmol) of NaClO₂ in 50 mL ofdistilled water are added to the mixture.

The reaction mixture is left at room temperature for 12 hours withstirring.

50 mL (approx. 500 mmol) of concentrated HCl are added.

The reaction mixture is adjusted to 5° C. and left under such conditionsfor 12 hours and the solid which forms is filtered, washed withdistilled water and methanol and subsequently dried.

2.44 g (yield 60%) of the product5,11,17,23,29,35,41,47-octa-hydroxycarbonyl-calix[8]arene (10) areobtained as a brown solid.

2.44 g (2.03 mmol) of5,11,17,23,29,35,41,47-octa(hydroxycarbonyl)calix[8]arene (10), 1 mL (10mmol) of concentrated H₂SO₄ and 200 mL (5 mol) of methanol areintroduced under an inert atmosphere into a 500 mL 3-necked glass flaskfitted with a mechanical stirrer, thermometer and condenser. The mixtureis adjusted to reflux while being stirred and left for 24 hours undersuch conditions.

The solvent is removed under reduced pressure and the resultant solid isrecrystallised from methanol and subsequently dried.

2.58 g (yield 97%) of the product5,11,17,23,29,35,41,47-octa-methoxycarbonyl-calix[8]arene (11) areobtained as a brown solid.

2.58 g (1.97 mmol) of5,11,17,23,29,35,41,47-octa-methoxycarbonyl-calix[8]arene (11), 5.10 g(22.3 mmol) of 4-(bromomethyl)methyl benzoate, 1.59 g (9.58 mmol) of KI,4.11 g (9.58 mmol) of K₂CO₃ and 50 mL of acetone are introduced under aninert atmosphere to a 100 mL 3-necked flask fitted with a stirrer,thermometer and condenser. The mixture is adjusted to reflux while beingstirred and maintained for 48 hours under such operating conditions.

After cooling to room temperature, 50 mL (50 mmol) of 1N HCl are added,the mixture is stirred and extracted with toluene in a separatingfunnel, separating the organic phase from the aqueous phase.

The solvent is removed under reduced pressure, resulting in a brownsolid.

Once dried, the product is recrystallised from methanol.

2.72 g (yield 55.3%) of the product,5,11,17,23,29,35,41,47-octa-methoxycarbonyl-49,50,51,52,53,54,55,56-octa[4-(methoxycarbonyl)benzyloxy]calix[8]arene(12) are obtained.

Example 10: Preparation of the Hydrogenated Isoprene-Styrene StarPolymer from the Calixarene of the Formula (12)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 1.2 g of tetrahydrofuran arethen added. The solution is then thermostated to 40° C. Once saidtemperature has been reached, 0.82 g of n-butyllithium in a cyclohexanesolution (12.80 mmol) are added. After 20 minutes, once styreneconversion is complete, 423 g of isoprene are added. After 30 minutes,once isoprene conversion is complete, 1.00 g (0.400 mmol) of thecalixarene of the formula (12) are added in a tetrahydrofuran solution.The reaction mixture is then maintained at a temperature of 40° C. for 1h.

The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The solution is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h and 30 minutes. Thesolution is then transferred into a tank, has antioxidants (2.6 g ofIrganox 565 and 17.0 g of Irgafos 168) added and is subsequentlytransferred into a stripping system in which the solvent is removed bysteam; the resultant granular product is then dried in a vacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 1.

Example 11: Preparation of the Hydrogenated Butadiene-Styrene StarPolymer from the Calixarene of the Formula (12)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 95 g of tetrahydrofuran are thenadded. The solution is then thermostated to 40° C. Once said temperaturehas been reached, 0.82 g of n-butyllithium in a cyclohexane solution(12.80 mmol) are added. After 20 minutes, once styrene conversion iscomplete, 423 g of 1,3-butadiene are added. After 30 minutes, oncebutadiene conversion is complete, 1.00 g (0.400 mmol) of the calixareneof the formula (12) are added in a tetrahydrofuran solution. Thereaction mixture is then maintained at a temperature of 40° C. for 1 h.The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The mixture is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h while being stirred. Thesolution is then transferred into a tank, has antioxidants (2.6 g ofIrganox 565 and 17.0 g of Irgafos 168) added and is subsequentlytransferred into a stripping system in which the solvent is removed bysteam; the resultant granular product is then dried in a vacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 2.

Example 12: Synthesis of the Calixarene of the Formula (16)

A calix[8]arene derivative which may be used according to a furtherpreferred embodiment of the present invention for synthesising starpolymers is5,11,17,23,29,35,41,47-octa-(3-triethoxysilylpropyl)-49,50,51,52,53,54,55,56-octa-(3-triethoxysilylpropoxy)calix[8]arene,which may be represented by the structure (16):

4.10 g (4.84 mmol) of calix[8]arene (3), the synthesis of which isdescribed in Example 1, 10.1 mL (116 mmol) of bromoallyl, 3.3 g (59mmol) of KOH, 1.5 mL of PEG 600, 15 mL of distilled water and 15 mL ofchloroform are introduced under an inert atmosphere into a 100 mL3-necked flask fitted with a stirrer, thermometer and condenser. Themixture is kept at room temperature for 24 hours under an inertatmosphere. 75 mL (75 mmol) of 1N HCl are added, the mixture is stirredand extraction performed with chloroform, separating the organic phasefrom the aqueous phase in a separating funnel.

The solvent is removed under reduced pressure, resulting in a whitesolid.

Once dried, the product is recrystallised from methanol. 4.07 g (yield72%) of the product 49,50,51,52,53,54,55,56-octa-allyloxycalix[8]arene(13) are obtained. 4.07 g (3.49 mmol) of49,50,51,52,53,54,55,56-octa-allyloxycalix[8]arene (13) and 50 mL ofN,N-diethylaniline are introduced under an inert atmosphere into a 100mL 3-necked flask fitted with a stirrer, thermometer and condenser. Themixture is adjusted to reflux while being stirred and maintained undersuch conditions for 2 hours.

After cooling to room temperature, 250 mL of ice and 250 mL (250 mmol)of 1N HCl are added.

The mixture is filtered and the solid product is recrystallised from2-propanol, resulting in 3.01 g (yield 74%) of5,11,17,23,29,35,41,47-octa-allyl-calix[8]arene (14). 3.01 g (2.58 mmol)of 5,11,17,23,29,35,41,47-octa-allyl-calix[8]arene (14), 7.5 mL (86mmol) of bromoallyl, 2.44 g (44 mmol) of KOH, 1 mL of PEG 600, 10 mL ofdistilled water and 10 mL of chloroform are introduced under an inertatmosphere into a 50 mL 3-necked flask fitted with a magnetic stirrer,thermometer and condenser. The mixture is kept at room temperature for24 hours under an inert atmosphere.

50 mL (50 mmol) of 1N HCl are added, the mixture is stirred andextraction performed with chloroform, separating the aqueous phase fromthe organic phase in a separating funnel.

The solvent is removed under reduced pressure, resulting in a whitesolid.

Once dried, the product is recrystallised from methanol.

2.61 g (yield 68%) of the product5,11,17,23,29,35,41,47-octa-allyl-49,50,51,52,53,54,55,56-octa-allyloxycalix[8]arene(15) are obtained. 2.61 g (1.75 mmol) of5,11,17,23,29,35,41,47-octa-allyl-49,50,51,52,53,54,55,56-octa-allyloxycalix[8]arene(15), 7.74 mL (42 mmol) of triethoxysilane, 100 mg (0.19 mmol) ofhydrogen hexachloroplatinate(VI) hexahydrate and 50 mL of toluene areintroduced under an inert atmosphere into a 100 mL 3-necked glass flaskfitted with a stirrer, thermometer and condenser. The mixture isadjusted to reflux while being stirred and maintained under suchconditions for 16 hours.

The mixture is hot filtered and the solvent present in the filtrate isremoved under reduced pressure.

Once dried, the product is recrystallised from heptane. 5.05 g (yield70%) of the product5,11,17,23,29,35,41,47-octa-(3-triethoxysilylpropyl)-49,50,51,52,53,54,55,56-octa-(3-triethoxysilylpropoxy)calix[8]arene(16) are obtained.

Example 13: Preparation of the Hydrogenated Butadiene-Styrene StarPolymer from the Calixarene of the Formula (16)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 95 g of tetrahydrofuran are thenadded. The solution is then thermostated to 40° C. Once said temperaturehas been reached, 0.82 g of n-butyllithium in a cyclohexane solution(12.80 mmol) are added. After 20 minutes, once styrene conversion iscomplete, 423 g of 1,3-butadiene are added. After 30 minutes, oncebutadiene conversion is complete, 1.10 g (0.267 mmol) of the calixareneof the formula (16) are added in a tetrahydrofuran solution. Thereaction mixture is then maintained at a temperature of 40° C. for 1 hand 15 minutes.

The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The solution is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h while being stirred. Thesolution is then transferred into a tank, has antioxidants (2.6 g ofIrganox 565 and 17.0 g of Irgafos 168) added and is subsequentlytransferred into a stripping system in which the solvent is removed bysteam; the resultant granular product is then dried in a vacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 2.

Example 14: Preparation of a Second Hydrogenated Butadiene-Styrene StarPolymer from the Calixarene of the Formula (16)

8 kg of anhydrous cyclohexane are introduced under an inert gasatmosphere (0.5 bar, N₂) into a 15 litre reactor equipped with a heatingjacket and stirrer. 47 g of styrene and 95 g of tetrahydrofuran are thenadded. The solution is then thermostated to 40° C. Once said temperaturehas been reached, 2.47 g of n-butyllithium in a cyclohexane solution(38.56 mmol) are added. After 20 minutes, once styrene conversion iscomplete, 423 g of 1,3-butadiene are added. After 30 minutes, oncebutadiene conversion is complete, 3.31 g (0.803 mmol) of the calixareneof the formula (16) are added in a tetrahydrofuran solution. Thereaction mixture is then maintained at a temperature of 40° C. for 1 hand 15 minutes.

The solution is then transferred, still under an inert gas atmosphere,into another 15 litre reactor, equipped with a heating jacket andstirrer, which is set up for hydrogenation. 1.61 g ofbutylethylmagnesium in a heptane solution and 1.22 g ofbis-cyclopentadienyltitanium dichloride in a cyclohexane suspension areadded. The solution is then placed under hydrogen pressure (15 bar) andmaintained at a temperature of 120° C. for 1 h while being stirred. Thesolution is then transferred into a tank, has antioxidants (2.6 g ofIrganox 565 and 17.0 g of Irgafos 168) added and is subsequentlytransferred into a stripping system in which the solvent is removed bysteam; the resultant granular product is then dried in a vacuum oven.

The characteristics of the resultant hydrogenated star polymer are shownin Table 2.

TABLE 1 HYDROGENATED ISOPRENE-STYRENE STAR POLYMERS AND CHARACTERISTICSTHEREOF Product Example 2 Example 4 Example 8 Example 10 Type of coreCalixarene Calixarene Calixarene Calixarene (5) (6) (8) (12) Calixarenestructure R₁ —C₆H₁₃ —CH₂(CH₆H₅)COOCH₃ —(CH₂)₃Si(OC₂H₅)₃—CH₂(CH₆H₅)COOCH₃ R₂ —CH₂Cl —C(CH₃)₃ —C(CH₃)₃ —COOCH₃ R₃ H H H H R₄ H HH H R₅ H H H H R₆ H H H H n 8 8 8 8 Polymer segment structure MonomersIsoprene- Isoprene-styrene Isoprene-styrene Isoprene-styrene styrene %hydrogenation 95 93 94 94 % by weight styrene 10 10 10 10 Polymerproperties Mw * 10³, dalton (a) 280 345 480 609 Mw * 10³, dalton (a) 224278 384 483 Mw * 10³ polymer 70 43 40 39 segments, dalton (a) Mw/Mn 1.251.24 1.25 1.26 Theoretical number 8 16 24 32 of polymer segments (a)values obtained by GPC/UV

TABLE 2 HYDROGENATED BUTADIENE-STYRENE AND BUTADIENE STAR POLYMERS ANDCHARACTERISTICS THEREOF EXAMPLES 15-25: LUBRICANT FORMULATIONS ProductExample 5 Example 6 Example 11 Example 13 Example 14 Type of coreCalixarene (6) Calixarene (6) Calixarene (12) Calixarene (16) Calixarene(16) Calixarene structure R₁ —CH₂(CH₆H₅)COOCH₃ —CH₂(CH₆H₅)COOCH₃—CH₂(CH₆H₅)COOCH₃ —(CH₂)₃Si(OC₂H₅)₃ —(CH₂)₃Si(OC₂H₅)₃ R₂ —C(CH₃)₃—C(CH₃)₃ —COOCH₃ —(CH₂)₃Si(OC₂H₅)₃ —(CH₂)₃Si(OC₂H₅)₃ R₃ H H H H H R₄ H HH H H R₅ H H H H H R₆ H H H H H n 8 8 8 8 8 Polymer segment structureMonomers butadiene-styrene butadiene butadiene-styrene butadiene-butadiene-styrene styrene % 1,2-vinyl 55 54 55 53 54 % hydrogenation 9999 98 98 99 % by weight styrene 10 0 10 10 10 Polymer properties Mw *10³, dalton (a) 354 343 600 807 340 Mw * 10³, dalton (a) 295 281 480 621274 Mw * 10³ polymer 42 41 38 37 14 segments, dalton (a) Mw/Mn 1.20 1.221.25 1.3 1.24 Theoretical number of 16 16 32 48 48 polymer segments (a)values obtained by GPC/UV

The solutions of star polymers were prepared in Group I Solvent Neutral150 base oil (eni SN 150). Dissolution was carried out by heating thebase oil to a temperature of 130° C., adding the polymer and stirring atthis temperature until dissolution was complete. Tables 3 and 4 show theconcentrations of the star polymers in the base oil. Using the sameoperating conditions, solutions in base oil SN 150 were then prepared ofthe commercial product Infineum Shellvis 260 (SV 260), which is ahydrogenated styrene-isoprene star polymer with a PDVB core, and of thecommercial product eni MX 4006, which is a linear ethylene-propylenecopolymer. Table 5 shows the concentrations of the commercial polymersin the base oil.

The following parameters, shown in Tables 3, 4 and 5, were determined onthe solutions of the polymers in the base oil:

-   -   shear stability index (method CEC-L-14-93);    -   thickening power.

The shear stability index was determined on a solution made up of 10% byweight of the polymer solution in base oil and by 90% by weight of baseoil SN 150.

Thickening power is calculated as the difference between the kinematicviscosity value at 100° C. of the 1% by weight polymer solution in SN150 and the kinematic viscosity value at 100° C. of the SN 150 oil.

Using the concentrated solutions of polymers as viscosity index-improveradditives, corresponding engine lubricating oils of viscosity grade SAE10W-40 of the following composition, expressed as percentage by weightrelative to the lubricating oil, were prepared:

-   -   base oils: 79.1% by weight;    -   additive package (DI package): 13.8% by weight;    -   viscosity index (VI) improver: 7% by weight;    -   pour point depressant (PPD) additive: 0.1% by weight.

50 parts per million (ppm) of foam inhibitor were also added to thelubricant.

The additive package used is a mixture of the following additives:dispersants, detergents, antioxidants and antiwear additives.

The following parameters were determined on the lubricating oils:

-   -   kinematic viscosity at 100° C. (method ASTM D 445)    -   kinematic viscosity at 40° C. (method ASTM D 445)    -   viscosity index (method ASTM D 2270)    -   CCS viscosity at −25° C. (method ASTM D 5293)    -   MRV viscosity at −30° C. (method ASTM D 4684)    -   MRV yield stress (method ASTM D 4684)    -   percentage viscosity loss by depolymerisation (method CEC        L-14-93)    -   gelation index (method ASTM D 5133)    -   gelation temperature (method ASTM D 5133)    -   HTHS viscosity (method CEC L-36-90)    -   pour point (method ASTM D 6892)    -   high-temperature deposits (method ASTM D 7097).

Tables 3, 4 and 5 show the results.

TABLE 3 LUBRICANT FORMULATIONS WITH HYDROGENATED ISOPRENE- STYRENE STARPOLYMERS Example Example Example Example Formulations 15 16 17 18Polymer Example 2 Example 4 Example 8 Example 10 Thickening power at100° C. (cSt) 6.6 7.6 9.6 11.5 (1% by weight polymer in SN 150)Concentrated solution of the polymer in base oil Polymer content 12.010.45 8.3 6.9 (% by weight) Base oil SN 150 (% by weight) 88.0 89.5591.7 93.1 Shear stability index (%) 23 7 13 17 Composition andproperties of 10W-40 oil Concentrated solution of polymer (VI 7 7 7 7improver) (% by weight) Base oils (% by weight) 79.1 79.1 79.1 79.1Additive package 13.8 13.8 13.8 13.8 (% by weight) Pour point depressant0.1 0.1 0.1 0.1 (% by weight) Kinematic viscosity at 40° C. (cSt) 92.0592.26 92.14 91.50 Kinematic viscosity at 100° C. (cSt) 13.71 13.78 13.7813.62 Viscosity index 151 152 152 151 HTHS viscosity (cP) 3.72 3.85 3.913.95 CCS viscosity at −25° C. (cP) 6900 6650 6400 6350 MRV viscosity at−30° C. (cP) 28200 26600 26500 25600 MRV yield stress <35 <35 <35 <35Viscosity loss by depolymerisation (%) 11.5 3.6 6.7 8.7 Gelation index4.1 4.5 4.5 4.6 Gelation temperature (° C.) −29.8 −29.5 −29.1 −28.1 Pourpoint (° C.) −39 −39 −39 −39 Total TEOST MHT deposits (mg) 28.5 25.022.6 21.4

TABLE 4 LUBRICANT FORMULATIONS WITH HYDROGENATED BUTADIENE- STYRENE ANDBUTADIENE STAR POLYMERS Example Example Example Example ExampleFormulations 19 20 21 22 23 Polymer Example 5 Example 6 Example 11Example 13 Example 14 Thickening power at 100° C. (cSt) 6.3 6.4 9.5 12.46.2 (1% by weight polymer in SN 150) Concentrated solution of thepolymer in base oil Polymer content 12.40 12.20 8.20 6.30 12.40 (% byweight) Base oil SN 150 (% by weight) 87.60 88.80 92.80 93.70 96.6 Shearstability index (%) 9 10 22 32 3 Composition and properties of 10W-40oil Concentrated solution of polymer 7 7 7 7 7 (VI improver) (% byweight) Base oils (% by weight) 79.1 79.1 79.1 79.1 79.1 Additivepackage 13.8 13.8 13.8 13.8 13.8 (% by weight) Pour point depressant 0.10.1 0.1 0.1 0.1 (% by weight) Kinematic viscosity at 40° C. (cSt) 91.1592.55 91.30 93.45 92.46 Kinematic viscosity at 100° C. (cSt) 13.65 13.8213.60 13.86 13.77 Viscosity index 152 152 151 151 151 HTHS viscosity(cP) 3.95 3.90 3.86 3.75 3.93 CCS viscosity at −25° C. (cP) 6800 67506500 6300 6850 MRV viscosity at −30° C. (cP) 27300 26500 25000 2340027500 MRV yield stress <35 <35 <35 <35 <35 Viscosity loss bydepolymerisation 4.8 5.3 11.7 17.1 1.6 (%) Gelation index 4.2 4.8 4.34.4 4.3 Gelation temperature (° C.) −28.9 −27.9 −26.0 −25.9 −26.0 Pourpoint (° C.) −42 −42 −42 −42 −42 Total TEOST MHT deposits (mg) 25.1 32.524.7 23.6 24.0

TABLE 5 LUBRICANT FORMULATIONS WITH COMMERCIAL POLYMERS MX 4006 AND SV260 Comparative Comparative Formulations Example 24 Example 25 PolymerMX 4006 SV 260 Thickening power at 100° C. (cSt) 5.2 7.5 (1% by weightpolymer in SN 150) Concentrated solution of the polymer in base oilPolymer content 13.05 10.55 (% by weight) Base oil SN 150 (% by weight)86.95 89.45 Shear stability index (%) 25 10 Composition and propertiesof 10W-40 oil Concentrated polymer solution 7 7 (VI improver) (% weight)Base oils (% by weight) 79.1 79.1 Additive package 13.8 13.8 (% byweight) Pour point depressant 0.1 0.1 (% by weight) Kinematic viscosityat 40° C. (cSt) 94.65 91.28 Kinematic viscosity at 100° C. (cSt) 13.9613.69 Viscosity index 151 152 HTHS viscosity (cP) 4.01 3.87 CCSviscosity at −25° C. (cP) 6780 6671 MRV viscosity at −30° C. (cP) 2150029300 MRV yield stress (mPa) <35 <35 Viscosity loss by depolymerisation(%) 11 5.2 Gelation index 5.3 4.7 Gelation temperature (° C.) −12.8−28.9 Pour point (° C.) −36 −39 Total TEOST MHT deposits (mg) 31.7 25.7On the basis of the results shown in Tables 3 and 4 and 5, it is clearthat the radial polymers of the present invention with a central coremade up of calixarenes have characteristics, such as thickeningcapacity, mechanical shear stability, oxidation stability and resistanceto the formation of deposits and low-temperature behaviour, which makethem highly suitable for use as viscosity index-improver additives inlubricating oils.

In particular, the polymer (Example 4) used in the formulation ofExample 16, made up of a calixarene core to which are linked 16hydrogenated isoprene-styrene polymer segments, exhibits mechanicalshear stability (shear stability index, viscosity loss bydepolymerisation) which is better than that of the commercial starproduct SV 260 (Comparative Example 26) which is made up of the sametype of polymer segments, but with a PDVB core. Using the samecalixarene of Example 4, but introducing 16 butadiene-styrene orpolybutadiene polymer segments, gives rise to star polymers (Examples 5and 6) which, when used in the formulations of Examples 19 and 20,exhibit thickening power and mechanical shear stability values which aregood, but slightly worse than those obtained in Example 16. It isnevertheless preferred to use butadiene rather than isoprene for reasonsof cost and commercial availability. Furthermore, introducing copolymerscontaining styrene (e.g. styrene-butadiene) onto the calixarene ensuresgreater resistance to the formation of deposits in comparison with thepolydiene segments (e.g. polybutadiene).

Increasing the number of hydrogenated polymer segments of a similarmolecular weight linked to the calixarene core, whether of thebutadiene-styrene copolymer series (Examples 19, 21, and 22) or of theisoprene-styrene copolymer series (Examples 16, 17 and 18), results in aconsiderable increase in thickening power at the cost of a slightreduction in mechanical shear stability. In particular, the starpolymers (Examples 10 and 13) used in the formulations of Examples 18and 22 and respectively made up of 32 and 48 polymer segments, havethickening power values more than twice those, together with comparablemechanical shear stability values, of the commercial product eni MX4006, a linear ethylene-propylene copolymer.

Furthermore, at identical thickening power, the larger is the number ofpolymer segments linked to the calixarene core, the better is mechanicalshear stability. This is because the polymer (Example 14) used in theformulation of Example 23, made up of 48 low molecular weighthydrogenated butadiene-styrene polymer segments, exhibits the samethickening power as, but much better shear stability than, the polymer(Example 5) used in the formulation of Example 19 which is made up of 16high molecular weight hydrogenated butadiene-styrene polymer segments.

The invention claimed is:
 1. Hydrogenated polymers with a radialstructure having a core made up of calixarenes of the general formula(I), to the core of which is linked a number P of hydrogenated linearpolymer segments selected from: hydrogenated homopolymers or copolymersof conjugated dienes; or hydrogenated copolymers of said conjugateddienes and monoalkenyl arenes, and mixtures thereof, said formula (I)being

in which: R₁, R₂, R₃ and R₄ are independently selected from hydrogen; agroup containing carbon and hydrogen; a group also containingheteroatoms in addition to carbon and hydrogen; a group also containingsilicon in addition to carbon, hydrogen and heteroatoms; one of the twosubstituents R₅ and R₆ is hydrogen, while the other may be hydrogen oralkyl, with a number of carbon atoms between 1 and 6; n is an integer inthe range between 4 and
 16. 2. Hydrogenated radial polymers according toclaim 1, in which the linear polymer segments are hydrogenatedhomopolymers or hydrogenated copolymers of conjugated dienes selectedfrom butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene,3-butyl-1,3-octadiene, 1-phenyl-1,3-butadiene and 1,3-hexadiene. 3.Hydrogenated radial polymers according to claim 2, in which the linearpolymer segments are selected from homopolymers or copolymers ofbutadiene and isoprene.
 4. Hydrogenated radial polymers in which thelinear polymer segments are hydrogenated copolymers of the conjugateddienes according to claim 2 and of monoalkenyl arenes selected fromstyrene, ortho-methylstyrene, para-methylstyrene, meta-methylstyrene,tert-butylstyrene and monovinylnaphthalene.
 5. Hydrogenated radialpolymers according to claim 4, in which the linear polymer segments arehydrogenated copolymers of butadiene and styrene, or hydrogenatedcopolymers of isoprene and styrene.
 6. Hydrogenated radial polymersaccording to claim 1, in which R₁ and R₂ may be selected from: an alkylhaving a number of carbon atoms between 1 and 24; or a group alsocontaining heteroatoms in addition to carbon and hydrogen and having anumber of carbon atoms between 1 and 16; or a group also containingsilicon in addition to carbon, hydrogen and heteroatoms in which thenumber of carbon atoms varies between 5 and 21; or an unsaturatedhydrocarbon group, with or without heteroatoms, having a number ofcarbon atoms between 2 and
 16. 7. Hydrogenated radial polymers accordingto claim 1 in which R₃, R₄, R₅ and R₆ are simultaneously hydrogen. 8.Hydrogenated radial polymers according to claim 1, in which P is between4 and
 72. 9. Hydrogenated radial polymers according to claim 1, in whichthe weight-average molecular weight (M_(W)) of each of the hydrogenatedlinear polymer segments which make up the hydrogenated radial polymer isbetween 10000 and
 200000. 10. Hydrogenated radial polymers according toclaim 1, in which the weight-average molecular weight (M_(W)) of thehydrogenated radial polymers is between 100000 and
 2000000. 11. Asynthesis method for the radial polymers according to claim 1 whichcomprises the following steps: i. synthesising a calixarene of thegeneral formula (I); ii. preparing the linear polymer segments byanionic polymerisation in solution of one or more conjugated dienes, orby copolymerisation of one or more conjugated dienes and a monoalkenylarene, in the presence of an ionic initiator to form a living anionicpolymer; iii. reacting the living anionic polymer obtained in (ii) withthe calixarene synthesised in (i) to form a polymer with a radialstructure; and iv. reacting, by selective hydrogenation, the olefinicunsaturations present in the radial polymer obtained in (iii) to obtaina hydrogenated radial polymer.
 12. A synthesis method for the radialpolymers according to claim 11, in which the living polymers are thosearising from the copolymerisation of a conjugated diene with amonoalkenyl arene, and characterised by a monalkenyl arene contentbetween 3% by weight and 30% by weight relative to the total weight ofthe copolymer, and a diene content between 97% by weight and 70% byweight relative to the total weight of the copolymer.
 13. A methodaccording to claim 12, in which the living polymers are those arisingfrom the copolymerisation of butadiene and styrene, and arecharacterised by a styrene content between 5% by weight and 25% byweight relative to the total weight of the copolymer and a butadienecontent between 95% by weight and 75% by weight relative to the totalweight of the copolymer.
 14. A method according to claim 11, in whichthe quantity of calixarene added in the coupling reaction of the livinganionic polymer with the calixarene in step (iii) is between 0.8/P moland 1.2/P mol per mol of living polymer.
 15. A method according to claim11, in which the coupling reaction of the living anionic polymer withthe calixarene in step (iii) is carried out in the presence of an inertsolvent selected from aliphatic hydrocarbons, aromatic hydrocarbons andethers.
 16. A method according to claim 15, in which the inert solventis the same as that used in step (ii).
 17. A method according to claim11, in which the temperature at which the coupling reaction of theliving anionic polymer with the calixarene is carried out in step (iii)is between 0° C. and 150° C., and said reaction is carried out under aninert atmosphere at an absolute pressure in the range between 0.5 and 10atm.
 18. A method according to claim 11, in which the radial polymerobtained in reaction stage (iii) is hydrogenated in reaction step (iv)in such a way that the degree of hydrogenation of the initially presentolefinic unsaturations is greater than 85%.
 19. The hydrogenatedpolymers with a radial structure according to claim 1 wherein one of thetwo substituents R5 and R6 is hydrogen, while the other is an alkyl,with a number of carbon atoms between 1 and 6.